Umbilical blood pH, Apgar scores, and early neonatal mortality

Abstract

For several decades Apgar scores and umbilical blood pH sampling have been routinely used in the assessment of newborns. The aim of this study was to examine the prognostic value of neonatal survival using population-based data and to put these analyses into context with international studies. Data from 513,135 live births from the Perinatal Birth Register of Hesse, 1990 - 1999, were used. Death in the first week of life (early neonatal death) was used as endpoint of analyses. Receiver operator characteristic analyses were employed to compare the prognostic value of Apgar scores and umbilical blood pHs independently of cutoffs used. Scores and umbilical blood pH showed a strong association with early neonatal morality. The relative risk of early neonatal mortality in term infants with scores 0 - 3 yields a relative risk of 1193 (95 % confidence interval = 801 - 1778) compared with babies born with scores 7 - 10. Scores at 1, 5, and 10 minutes were superior in predicting early neonatal mortality compared to umbilical blood pH, independent of cutoffs used. Scores remain essential in the prediction of early neonatal survival. Umbilical blood pH is also strongly and significantly associated with early neonatal death, even though it is much less pronounced than the score. The poor mortality prediction of umbilical blood pH sampling in Hesse compared with umbilical blood pH sampling in a large American delivery unit with a highly standardized measuring routine may be explained by a lower proportion of extremely acidotic infants or may be attributable to a decreased proportion of or to a less unified or less reliable measurement of the umbilical blood pH in Hesse.